Antonio Conte hasn't developed backup plan for struggling Diego Costa

Even the most cynical and exacting of football supporters would find it hard to criticise Antonio Conte's tenure at Chelsea. His team embarked on a 13-match winning streak in his debut Premier League season. He became the first manager to win both league matches against a Pep Guardiola side and established daylight between Chelsea at the top of the table and the chasing pack. And all this came after a miserable title defence and a faltering start to the season that made a viable title challenge appear to be nothing more than wishful thinking.

But no team or manager is ever flawless and, for Conte, the one area of possible myopia concerns his central striker.

There is no doubting that on his day, Diego Costa is one of the most brutally effective strikers in Europe. When the mood takes him and his form is at its height, he is a one-man wrecking ball that dominates defenders. Capable of running the channels, holding the ball up, creating for others and scoring from impossible positions, a fully charged Costa is an invaluable asset.

But when he is out of sorts, he can be a liability. The energy doesn't diminish, but it is rarely channelled in the right direction. His brain seems to scramble and he finds himself easily antagonised by wily opponents, something Manchester United's Marcos Rojo managed both on Sunday and in the FA Cup quarterfinal meeting in March. Distracted by his own rage, he then struggles to control simple passes and often fails to choose the correct decision in pivotal situations, usually opting to hang on to the ball rather than releasing the ball to a better-placed teammate.

Normally this wouldn't be a huge problem. Form is a transient thing, after all. The issue is that Conte has nobody else he can trust to play in that position and he only has to look in the mirror to find the reason for this. Michy Batshuayi became Chelsea's third-most expensive signing after Fernando Torres and Andriy Shevchenko when he joined from Marseille last summer for £33 million. But much like the Chelsea careers of the two illustrious strikers above him in the list, he has struggled to make an impression.

Despite the outlay, Conte has been highly reluctant to use the young Belgian, preferring to deploy Eden Hazard as a roving front man in Costa's absence. The exact reasons for this are unclear, but it surely cannot be based basis on Batshuayi's sparse Premier League outings. Officially he has appeared in 17 of Chelsea's 32 Premier League games, a shade over half the campaign. That statistic, however, is misleading as has failed to start a single match, with all his appearances being as a substitute. He has been on the pitch for the sum total of 110 minutes. Given that there is no other obvious alternative to Costa, surely it would have made sense to give him more on-pitch experience, especially when the result in a game is already beyond doubt, so that he could step into the breach if and when required.

And yet Batshuayi's time at the club began in encouraging fashion. It was his towering leap and header that set up Costa for the decisive goal in a 2-1 win over West Ham on the opening weekend of the season. And it was his strike that drew Chelsea level in the 80th minute at Watford on the following weekend before Costa grabbed another winner. Since then he has scored four goals across various domestic cup matches but contributed nothing else of note, largely due to a lack of opportunity.

Conte's decision to severely limit Batshuayi's game time always felt strange, but has been forgiven due to the extraordinary job that he has done in every other area of the team. Now, though, the issue is clear with Costa's form utterly wretched. The Spain international's display at Old Trafford was the latest in a series of sub-standard performances that have characterised his play since the fracas over his failed move to China in January.

Normally, the manager would deal with this by sidelining his player and replacing him with somebody else. Unfortunately, with precious few minutes under his belt, it would almost be unfair to draft Batshuayi into the starting lineup and burden him with leading the line at this particular juncture. For the first time in the title race, Chelsea are now feeling some genuine pressure, so now is not the time to place faith in their callow striker, whose confidence must be shattered following a difficult season.

So it seems that the manager has no choice but to continue with Costa and hope that he rediscovers what made him such an unstoppable force in the first four months of the campaign. To date, almost everything that Conte has touched has turned to gold, and everyone at Chelsea will be praying that it includes a resurgence from his main striker over the next six matches.

Phil is one of ESPN's Chelsea bloggers. You can follow him on Twitter @PhilLythell.